The present invention relates to a fill-up control valve structure provided in a ventilation passage connecting a fuel tank and a canister, and more particularly to the structure for a fill-up control valve capable of functioning as a fuel leak prevention valve for suppressing pressure change occurring in a fuel tank.
An automotive vehicle is usually equipped with a fuel tank storing the fuel to be supplied into a combustion chamber of an engine. The fuel tank is equipped with a ventilation system so that air is introduced into or discharged from the inside space of the fuel tank in accordance with increase or decrease of the fuel amount in the fuel tank. The ventilation system connects the inside space of the fuel tank and the canister. Therefore, if the fuel tank is filled with the fuel, there is the possibility that the fuel may overflow into the canister. If the canister is soaked with the fuel, the canister will be no longer usable. In view of the above, a fill-up control valve is provided at the upper portion of the fuel tank to shut off the ventilation system when the fuel tank is filled up to prevent the air and the fuel from being conveyed into the canister.
Furthermore, in addition to the above-described fill-up control valve, the fuel tank is equipped with a fuel leak prevention valve which is usually in an opened condition to connect the inside space of the fuel tank to the outside air to eliminate or adjust the pressure change occurring in the fuel tank and is closed in an event that the automotive vehicle is inclined or rolled over.
In general, the fuel tank is installed in a limited dead space available in the automotive vehicle which requires many essential engine components to be installed together with the fuel tank. Thus, the fuel tank tends to be configured into a thin and irregular shape. Accordingly, when the automotive vehicle is inclined, there is the possibility that a thin fuel tank may have a closed inside space temporarily at its front or rear end depending on the direction of vehicle inclination. If the fuel leak prevention valve is not located at this temporarily formed closed space, the fuel tank may deform.
Therefore, some of conventional fuel tanks are equipped with two or more fuel leak prevention valves. Furthermore, a fuel pump unit is attached to the fuel tank.
FIG. 9 shows a conventional fuel tank with a fill-up control valve. A fuel tank 1, installed on an automotive vehicle, stores fuel to be supplied into an engine. A fill-up control valve A is disposed at the upper portion of the fuel tank 1. The fill-up control valve A is connected via a ventilation passage 5 to a canister 4. The fuel tank 1 has a fuel feed pipe 3 with a filler cap 2 attached at its distal end so that the tank can be occasionally refilled with additional fuel via the fuel feed pipe 3.
The fuel tank 1 has a thin shape extending in a right-and-left direction in the drawing, with a recessed portion formed at its center. A fuel pump unit 6 and a fill-up control valve A are provided at the central recessed portion. Two fuel leak prevention valves B and C are disposed on swelled portions formed at the right and left sides of the fuel tank 1.
FIG. 7 shows the detailed arrangement of the fill-up control valve A. The fill-up control valve A includes a casing 10 provided inside the fuel tank 1, a float 11 disposed in the casing 10, a spring 12 giving a resilient force acting on the float 11 in the upward direction, a valve body 13 attached to the upper portion of the float 11, and a ventilation passage 5 communicating with the downstream side of the valve body 13 at one end and also communicating with the canister 4 at the other end.
The casing 10 has a hollow cylindrical shape with an opened top and an inside space defining a float chamber 17. A valve seat 15 is formed at the upper part of the casing 10. Furthermore, a plurality of vertical ribs 16, provided on the inner cylindrical surface of the casing 10 at equal angular intervals, cooperatively guide the up-and-down movement of the float 11. A bottom plate 19 having at least one ventilation hole 18 is attached to the bottom portion of the casing 10. The casing 10 has a flange 14 extending outward from its outer cylindrical surface. The flange 14 supports the casing 10 to the upper surface of the fuel tank 1.
The fill-up control valve A has the above-described arrangement. When the fuel is supplied into the fuel tank 1 via the fuel feed pipe 3, the fuel surface level in the fuel tank 1 rises. When the fuel surface level reaches the bottom plate 19, the fuel enters into the inside space of the casing 10 via the ventilation hole 18 of the bottom plate 19. The fuel pushes the float 11 upward. When the fuel surface level reaches a predetermined position in the float chamber 17, the valve body 13 provided on the upper surface of the float 11 is brought into contact with the valve seat 15. Upon the valve body 13 contacting with the valve seat 15, the ventilation passage 5 is closed. Then, the pressure in the fuel tank 1 starts increasing with progress of fuel supply and finally the fuel feed stops when the inside pressure reaches a predetermined level. The fuel surface level at this moment is referred to as “filled-up fuel surface level H.”
FIG. 8 shows a schematic arrangement of the fuel leak prevention valves B and C. The fuel leak prevention valve B is disposed at a higher position compared with the above-described fill-up control valve A. A small-diameter passage 20 connects the downstream side of a valve body 13′ to the ventilation passage 5 shown in FIG. 9. The valve body 13′ of the fuel leak prevention valves B and C is different in configuration from the valve body 13 of the fill-up control valve A. The rest of the arrangement of the fuel leak prevention valves B and C is substantially the same as that of the fill-up control valve A.
More specifically, as respective fuel leak prevention valves B and C are positioned high compared with the fill-up control valve A, these valves B and C are not closed during the fuel feeding operation and accordingly are always in the opened condition. When the fuel tank 1 is inclined, a closed space is temporarily formed at either upper part of the fuel tank 1. In such a case, each of the fuel leak prevention valves B and C, being disposed on the upper surface of the fuel tank 1 via a flange 14′, connects the temporarily closed space to the canister 4 via the small-diameter passage 20. Thus, the pressure change in the fuel tank 1 can be suppressed. Each of the fuel leak prevention valves B and C may sink in the fuel depending on the direction of the inclined fuel tank 1. In such a case, in the fuel leak prevention valve B or C, the float 11′ causes an upper shift movement and the valve body 13′ contacts with a valve seat 15′ to close the small-diameter passage 20. Thus, no fuel overflows into the canister 4. The rest of the arrangement of respective fuel leak prevention valves B and C, including a casing 10′, a spring 12′, a float chamber 17′, a ventilation hole 18′, and a bottom plate 19′, are substantially the same as those of the fill-up control valve A. (For example, referred to Japanese Patent Application Laid-open No. 8-258577(1996)).
In general, the fuel tank 1 is made of a material having the capability of protecting permeation of the fuel. On the other hand, the above-described fill-up control valve A and the fuel leak prevention valves B and C as well as the flange used to attach the fuel pump unit 6 to the fuel tank 1 are not made of such fuel-impermeable material. According to the above-described conventional fuel tank 1, the fill-up control valve A and the fuel leak prevention valves B and C are attached on the upper surface of the fuel tank 1. Thus, the above-described conventional fuel tank 1 has many fuel-permeable sources. The fuel permeation amount will increase. In recent years, the rubber packing and other sealing members tend to be replaced with low-permeable type materials. However, completely eliminating the permeation of fuel occurring through these fuel-permeable sources is impossible.
Furthermore, providing a plurality of fuel leak prevention valves or independently attaching the fuel pump unit 6 to the fuel tank 1 will increase the number of constituent parts and will complicate the assembling process. The production cost will increase accordingly.